Look for the 20h ROM and use the LG tool to flash it. You'll probably find links to both at XDA forums. (20g is also KitKat, but 20h seems to be the latest - that's what I got from AT&T a few days ago on a phone I'm repairing.)

Just for kicks, though, go to Settings/General/About Phone/Software Update. The phone I'm working on has a non-registered SIM, and it got the update via wifi anyway.